1. Field of Invention
The present invention relates to an improved method for mobility control. More specifically, it is concerned with the use of a heat treated lignosulfonate fluid for mobility control particularly during a water or micellar flood process and the like.
2. Description of the Prior Art
High molecular weight polymers are currently used for improving sweep in reservoirs caused by permeability contrast or by an unfavorable mobility ratio and the like. They are also employed as a mobility buffer in the micellar flood process. Various polymers have been proposed, tested, and used, particularly in recent field pilot tests of various so-called tertiary recovery processes, but experience has brought out some limitations. For example, of the two most frequently suggested polymer types, polyacrylamides and biopolymers, each have less than ideal behaviors. The polyacrylamides are highly sensitive to shear, temperature, and salinity of injection water. Biopolymers are subject to bacterial degradation and injectivity problems because of the cell walls which are produced along with the polymer during manufacture. Expensive diatomaceous earth filtration is frequently required to remove the cell walls prior to injecting the polymer. Both polymer types propagate poorly in tight rock. In addition to these technical shortcomings, the cost effectiveness of the prior art polymers (i.e., the cost per unit mobility reduction produced) can be improved. In view of the prior art polymers, there is considerable incentive to develop polymers that would be more effective and/or more economical.
Although lignosulfonates have been suggested and used successfully as gelable plugging fluids, up to this time they have been ineffective as viscosity builders unless high concentrations are used. However, at the greater than 30% concentration levels necessary for significant viscosity buildup, the expense is excessive.